A former Guantánamo Bay detainee who is a well-known advocate for the rights of terrorism suspects was arrested Tuesday on suspicion of Syria-related terrorism offenses, British police said.

West Midlands Police said Moazzam Begg was one of four people detained in the Birmingham area of central England.

Police said Begg, 45, is suspected of attending a terrorist training camp and facilitating terrorism overseas.

He was arrested along with a 44-year-old woman, her 20-year-old son, and a 36-year-old man — all suspected of facilitating terrorism overseas. Their names were not released.

Police in Britain do not usually name suspects until they are charged. The force said it was identifying Begg to the media “as a result of the anticipated high public interest.”

The four suspects were being questioned at a Birmingham police station and their homes searched.

Begg was arrested in Pakistan in 2002 and sent to the U.S. prison camp in Cuba.

He was released from Guantánamo in 2005 and became a director of the advocacy group Cage, formerly known as CagePrisoners.com.

He is a well-known figure who appears frequently in British media. On his Twitter account he identifies himself as “Director of Outreach for Cageprisoners advocating for the rights of those held unjustly in the War of Terror.”

Cage called Begg’s arrest a government attempt “to ensure that any travel to Syria is deemed suspicious” and to criminalize legitimate activism.

British officials say hundreds of Britons have traveled to Syria to join the battle against the forces of President Bashar Assad. Authorities fear they could present a risk when they return home after fighting with al-Qaida-affiliated groups.

British police have stepped up arrests over suspected Syria-related terrorism.

Begg has said that authorities revoked his British passport last year, even though his trips to Syria in 2012 were approved by Britain’s domestic intelligence service.

At Guantánamo, a Pentagon spokesman, Army Lt. Col. Todd Breasseale, said Defense Department officials were “aware of the arrest” and would discuss it “with the appropriate authorities.”

The Miami Herald’s Carol Rosenberg contributed to this report from Guantánamo.